Low-frequency infrared spectra of some phosphine-substituted group VI metal carbonyls

Abstract

The far-infrared spectra (700–130 cm.^–1) of phosphine-substituted Group VI metal carbonyl derivatives of the type M(CO)_{6 –x}(PPh₃)_x, and M(CO)_{6 –2y}(Diphos)_y, where M = Cr, Mo, and W; x= 1, 2, or 3; y= 1 or 2, and Diphos = 1,2-bisdiphenylphosphinoethane, are reported. By analogy with the spectra of the parent hexacarbonyls, infrared-active metal–carbon–oxygen bending and metal–carbon stretching modes of vibration are assigned and these occur in the ranges 700–500 and 500–300 cm.^–1, respectively. Absorptions observed in the region 200–130 cm.^–1 are tentatively assigned as metal–phosphorus stretching vibrations.